Effect of condensed tannins on growth performance, intestinal immune capacity and bacterial microbiomes of Lateolabrax japonicus

The objective of this study was to assess the effects of condensed tannins (CT) on growth performance and intestine health of juvenile Japanese seabass (Lateolabrax japonicus). Four diets were formulated to contain 0 (CT0), 100 (CT100), 200 (CT200) and 400 (CT400) mg/kg of pure CT isolated from grape seed. Quadruplicate groups of 20 fish were fed to apparent satiation two times daily during 56-days feeding trial. At the end of trail, the blood and intestine samples were collected to analyse serum metabolites, intestinal enzyme activity and histomorphology, and bacterial microbiomes of the fish. Results indicated that growth performance and intestinal histomorphology of fish were not affected by treatments. Fish fed CT200 and CT400 had lower (p < 0.05) serum lipopolysaccharide (LPS) than those fed CT0 and CT100. Activity of trypsin and Na+, K+-adenosine trisphosphatase (Na+, K+-ATPase) was lower (p < 0.05) in CT200 and CT400 than in CT0 and CT100. Over 93% of the sequences were classified within the Plesiomonas and Cetobacterium. The genera Plesiomonas increased (p < 0.05) and Cetobacterium decreased (p < 0.05) as dietary CT increase. Fish fed CT-containing diets had higher (p < 0.05) ACE, Chao 1 and Shannon bacterial diversity indices. A clear distinction of bacterial communities among treatments was noted as the plots cluster separately when the structure of bacterial communities was assessed using Bray-Curis distances. In conclusion, dietary CT up to 400 mg/kg did not affect growth performance but inhibited intestinal trypsin and Na+, K+-ATPase activities, decreased serum LPS and declined abundance of Cetobacterium. The increased bacterial diversity in fish fed CT-containing diets may due to the inhibitory effect of CT on Cetobacterium and Aeromonas, resulting in the increased genera such as Clostridium and Brevinema.

Automated summary

The study evaluated the effects of condensed tannins on growth performance and intestine health of juvenile Japanese seabass. Results showed that while growth performance and intestinal histomorphology were not significantly impacted, fish fed diets with higher CT levels had lower serum LPS, decreased enzyme activity, and changes in bacterial microbiomes.